Someone at SGI made a Flash generator. He gives away the binaries for free for several platforms. There is a free Perl frontend to the C API that drives the generator. It would be a great project to convince that author to give the Free Software world a chance to catch up to the Flash and Shockwave movement.
There are open sourced version of browser plug-ins and some semblance of releasing the file format has been attempted by Macromedia. But overall it's a very closed and proprietary thing.
